Industry experts say that ESBs are dead, but as Ira Gershwin wrote — it ain’t necessarily so.

Gartner VP Roy Schulte coined the term enterprise service bus (ESB) in 2002 during the technology’s early days, and just two years later some IT experts already declared it dead. More recently, ESB product sales have flatlined, as the centralized, hub-and-spoke IT environments ESBs support are replaced by loosely-coupled cloud middleware, namely iPaaS and MWaaS, said Elizabeth Golluscio, a Gartner analyst .

But enterprises aren’t dumping ESB products willy-nilly, because ESB products handle requirements newcomer technologies can’t. Also, enterprise IT has found that breaking up with monolithic ESB-based middleware is hard to do.

Middleware revenues will peak at $30 billion this year, but despite the double-digit pace of iPaaS and MWaaS investments their sales will account for only a fraction of that market. Most middleware spending will go to maintain and upgrade ESB and SOA infrastructures, as large enterprises continue to do complex integrations and messaging that iPaaS can’t handle such as data-intensive and hybrid integration processes, said Saurabh Sharma, principal analyst for Ovum, a UK IT research firm.

On the messaging side, an ESB product is best-suited for pub/sub messaging in asynchronous communications and message queues, Golluscio said. “The messaging model for integration or event handling is not something that the iPaaS tools do well yet,” she said. However, iPaaS vendors have pulled together classic integrations, API management and event mediations, and on the open source messaging side, Confluence and Kafka are coming on strong, she said.

Despite the strengths of on-premise ESB products, most of their capabilities will inevitably move to the cloud — but this is not a simple process. “It is very hard to move away from ESBs, which literally have tentacles connected to every important system in an enterprise IT environment,” Golluscio said. Change management factors and reaching consensus between business and IT ultimately slow down MWaaS adoption, Sharma noted. Both analysts say a shortage of ESB expertise is a hurdle.

To break up ESB product monoliths, some IT teams adopt a phased approach to focus on new integration projects with only MWaaS, Sharma said. Integration workloads that run on-premises gradually migrate to iPaaS, and developers will chip off ESB features into microservices.

In many cases, enterprise IT adds an iPaaS and an API management tool to their integration infrastructure, Golluscio said. They start with an ESB-based system, and use an Extract-Transfer-Load (ETL) tool for data integration, and then migrate to iPaaS and implement API management.

Reduced dependence on legacy ESB products is a challenge but pays dividends, with lower costs for both technology and staff. “The old joke was that the ESB middleware market was like the haves and the have-nots; only a certain number of companies had the money to buy and the resources to deal with ESBs,” Golluscio said.

iPaaS’ ease of use and pay-per-use attracts companies that lack the internal expertise or money for legacy ESBs. They certainly don’t require a deep bench of rocket scientists to use, Golluscio said.

“Finally, the democratization of enterprise tech has finally hit the integration space,” she said.

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